JOUKNAL or THE DePARTMEIST OF AgKICULTUKE. — J ULY, 1922. 



BASIC SLAG. 



The Change in its Composition. 



Report by Chas. F. Juritz, M.A., D.Sc, F.J.C. 

 Chief, Division of CheiiiistiA'. 



A CONSIDERABLE change has come over the composition of basic slag- 

 since the war, whereby its grade has been lowered. The subject has 

 been given serious attention in England, and the Imperial Minister 

 of Agriculture in July, 1920, appointed a committee to study the 

 basic slag problem, with Dr. E. J. Russell, the Director of the 

 Rothamsted Experimental Station, as chairman. Towards the close 

 of 1921 this committee submitted an interim report, which has not 

 yet been published. 



The change of composition is due to the fact that in the steel 

 industry the basic Bessemer process, of which basic slag was a by- 

 product, has now been superseded by the basic open-hearth process, 

 and the character of the by-product has been entirely altered, its 

 phosphate content having been halved. 



Investigations in England. 



The terms of reference placed before the Departmental Com- 

 mittee, which comprised steelmakers, fertilizer manufacturers, and 

 farmers, were " to consider the development and improvement of the 

 manufacture of basic slag and the extension of its use." The 

 committee has up to the present discussed such questions as these : 

 (1) the quantity of slag producable under present conditions ; (2) 

 how much slag can be advantageously utilized by farmers in Britain ; 

 (3) how the quantity or quality of the slag may be increased by 

 combining with the ordinary manufacture of steel some subsidiary 

 process; (4) what the agricultural value of the present quality of 

 slag is. 



(1) Before the war the annual output of high-grade slag in 

 Britain was 260,000 tons. In 1920 it was only 46,000 tons. It may 

 be of interest to tabulate the whole of the 1920 output a<'cording to 

 grade : — 



Over 15 per cent, phosphoric oxide 46,000 tons. 



12 per cent, and under 15 per cent 121,000 tons. 



10 per cent, and under 12 per cent 91,000 tons. 



7 per cent, and under 10 per cent 302,000 tons. 



5 per cent, and under 7 per cent 118,000 tons. 



Under 5 per cent 23,000 tons. 



Total 701,000 tons. 



